Is there a way to identify what might be considered key components to a Cougar's original build? If I'm looking at the purchase of one that according to the Marti report came with 3.00 Traction-Loc Rear Axle, can I determine if that is still on the car? Is this a "numbers matching" question?

Look for the tag on the rear and jack the car up, if when you spin one wheel the other goes the opposite direction it is most likely a conventional rear, if they both go the same way that indicates locking. Severe wear and damage can negate these results.